I'm a 56 year old Irish teacher - though not of any Science, so no homework involved here. Nothing in my textbook "Modern Chemistry", helps with this.

A mole of carbon is 12 grams of graphite and is approximately the volume of the lead in my pencil.A mole of nitrogen is about 14 grams, but it occupies a space of a litre, and it is a gas. Puzzling to me why we see (a) extraordinary rise in volume occupied and (b) why the change in matter.

If the volume change helps explain the change in matter, how do we account for the dramatic change in volume? After all, a mole of oxygen, nitrogen's neighbour, has the SAME volume as a mole of nitrogen, and yet the net change in the fundamental number of particles between 1 mole nitrogen, to 1 mole oxygen, is precisely the same as net difference between 1 mole carbon, 1 mole nitrogen.

Incidentally, I note that phosphorus and arsenic are in the same group as nitrogen. Using the table to predict their physical properties might lead me to believe they are gases too, but of course, they're not.

As it was already signaled several times: the property of the elements that is used as a key for arranging elements in the periodic table has (almost) no simple connection with their physical properties.

To use a (poor) analogy: imagine having handful of used crayons. You arrange them (using their colors) as in a rainbow. Does the position of the crayon in the arrangement tell you anything about its length?

As it was already signaled several times: the property of the elements that is used as a key for arranging elements in the periodic table has (almost) nothing to do with their physical properties.

To use a (poor) analogy: imagine having handful of used crayons. You arrange them (using their colors) as in a rainbow. Does the position of the crayon in the arrangement tell you anything about its length?

I'm sorry, but are you saying "This is simply the nature of nature". Is there no explanation to account for the change in the state of matter from carbon to nitrogen? I appreciate your time and patience.

Is there no explanation to account for the change in the state of matter from carbon to nitrogen?

Using electron structure (or configuration) of atoms of carbon we can explain why it is solid, we can explain - again starting from electron structure of atoms - why nitrogen is gaseous. But these are separate things. There is no continuity that will allow us to say "because of that and that state of matter changes".

To use another analogy (not much better than the previous one) it is like trying to predict whether 11 is divisible by 7 from the fact 10 is divisible by 2 and 5. There is no connection, even if 11 is a neighbor of 10.

In the case of some other elements being neighbors of the same kind as C and N such a continuity exists (for example, several consecutive metals having a higher and higher density as we move to the right), but it is rarely simple.

N2 makes a perfect chemical bond, if you understand it with molecular orbitals. This leaves little possibilities for more interactions. C2 in contrast isn't an excellent combination, with two electrons less, and while this molecule exists as a gas at high temperature, other combinations are energetically more favourable at room temperature, where more atoms are involved - graphite.

This isn't the whole picture. As you go down the so-called periodic table, molecules tend to stick better to an other. This explains why gases use to comprise lighter atoms and solids heavier ones. Or even, heavier atoms tend to make metals, where the molecules are huge - still a different reason.

"Next to an other" in the periodic table does not imply similar properties. Next to rare gases right and left, you have very reactive alkaline metals and halogens. Similar chemical properties are observed within columns instead. This similarity lets suppose compounds with similar chemical formulas exist but is a poor predictor for physical properties.

There should be a reason for the state changes between similar elements in regards to a couple particles . I can surely see the curious questions beanyboy would naturally come to on the thought .

I feel it's not very scientific to merely state it s the nature of the elements , not that anyone is.

I would probably attribute the changes to valence election numerals, bond types and orbital configurations and even nuances of spin at subatomic interactions for some of the elements then postulate weak nuc forces for some of the solid states of heavier elements.